<?php
function str_norm1($str) {
	$ret = str_split( $str );
	return $ret;
}

function str_norm2( $str ) {
//	return preg_split("//u", $str, -1, PREG_SPLIT_NO_EMPTY);
	return preg_split('//u', $str); 
}

$str = "Привет моЯ Дорогая і-І,.їЇ";
echo strtolower( $str )."\n";

$str2 = mb_strtolower( $str, 'UTF-8');
echo $str2."\n";

$str2 = preg_replace( '/[^а-яіїa-z0-9]/u', '', $str2 );
echo $str2."\n";


print_r( str_norm1($str) );
print_r( str_norm2($str) );
?>